Background

Mast cell disorders present a diagnostic challenge. Hereditary Alpha-Tryptasemia (HaT), defined by extra copies of the TPSAB1 gene leading to baseline elevated tryptase, is a predisposing factor. The coexistence of HaT with tissue infiltration complicates the distinction from other mast cell diseases.

Case Presentation and Genetic Confirmation

We report a 65-year-old female with two months of epigastralgia and recurrent urticaria and elevated serum tryptase (38ug/L). Molecular analysis for TPSAB1 confirmed a genotype consistent with HaT (\beta:\alpha / \beta:\alpha:\alpha).

Histological Findings and Diagnosis

The gastroscopy showed mild gastropathy. Histopathology of the gastro-duodenal biopsies was crucial, revealing a dense infiltration of mast cells (CD117+) in the lamina propria: > 80/HPF in the duodenum and > 30/HPF in the stomach. This profound infiltration suggests that symptoms were driven not solely by HaT, but also by a significant local mast cell pathology in the GI tract.

Discussion and Conclusion

This condition is rare and under-recognized by gastroenterologists, as non-specific GI symptoms are often confused with IBS or GERD. The correct diagnosis, leading to rapid symptom remission with famotidine and sodium cromoglycate, required integrating the clinical history, the HaT genetic finding, and a targeted histopathological examination of the GI biopsies. This case highlights the importance of ruling out mast cell proliferation in the GI tract in patients with unexplained abdominal symptoms and baseline elevated tryptase, regardless of an underlying genetic predisposition like HaT.